Definitive diagnosis of microsporidial infection relies on observing microsporidia in biopsy tissue, bodily fluid specimens, or stool examined by transmission electron microscopy. This method lacks sensitivity when performed on stool and is a very laborious and specialized procedure. Detection of microsporidia by light microscopic examination of stained stool specimens from patients with gastrointestinal infection allows rapid diagnosis in a routine clinical microbiology laboratory. Because microsporidia are not detected in traditional ova and parasite examinations of stool specimens, modifications of the trichrome stain are now available for the detection of microsporidia in stool specimens.We participated in an international diagnostic multicenter study to compare the sensitivity and specificity of the modified trichrome stain compared to the polymerase chain reaction. We received 50 specimens (both positive and negative) to stain with the modified trichrome stain and examine for the presence of microsporidial spores. The data from the 12 participating laboratories have been combined and the results of the study have been published as OBlinded, Externally Controlled Multicenter Evaluation of Light Microscopy and PCR for Detection of Microsporidia in Stool Specimens (J Clin Microbiol 1998;36:1814-1818).This study is completed.